CMS Energy (P/C Chart, news, volatility) is seeing 19x normal volume today, as shares trade nearly flat at 11.83. Bulk of the volume was an institutional buyer of 3100 Jan-10 10 puts for $1.175 tied to shares at 11.80, to create the largest block of open interest in the name. CMS traded near 9.20 in late Dec, and recently increased their dividend. Earnings due in late Feb and this buyer may be taking steps to protect his holdings given the recent rise in shares.